Automatic synchronizing system

ABSTRACT

In an automatic synchronizing system comprising a synchronizing circuit including a variable element, a sampling device and a synchronism control circuit which operates to differentiate the output from the sampling device to vary the variable element, to stop the variation of the variable element and to maintain the stopped condition, there is provided a control circuit responsive to the cessation of operation of either one of the synchronizing circuit or the sampling device to start either one of the synchronizing circuit, sampling device and the synchronism control circuit to continue to find a point of synchronism even in the absence of a synchronizing signal for a predetermined interval or even when the amplitude of the synchronizing signal is small. A time axis circuit may be added which may be controlled by the control circuit in the same manner.

[ Jan. 22, 1974 AUTOMATIC SYNCHRONIZING SYSTEM [7 5] Inventors: KozoUchida; Naohisa Nakaya; Koji Suzuki, all of Tokyo, Japan [73] Assignee:Iwata Electric Company, Tokyo,

Japan [22] Filed: Aug. 20, 1969 [21] App]. No.: 851,589

[30] Foreign Application Priority Data Aug. 23, 1968 Japan 43/59921 [52]US. Cl 315/19, 328/72, 328/179 [51] Int. Cl. HOlj 29/70 [58] Field ofSearch 328/63, 72, 73, 179, 151; 315/18, 19; 307/228 [56] ReferencesCited UNITED STATES PATENTS 2,863,055 12/1958 Kuehn et a1. 328/179 X2,980,858 4/1961 Grondin et a1 328/63 3,080,487 3/1963 Mellott et a1.328/63 X 3,153,762 10/1964 Johnson 328/63 3,213,375 10/1965 St. John328/63 conr cm scope, 1965.

Primary ExaminerMaynard R. Wilbur Assistant ExaminerI-l. A. BirmielAttorney, Agent, or Firm-Charles E. Pfund, Esq.; Chittick. Thompson &Pfund [57] ABSTRACT In an automatic synchronizing system comprising asynchronizing circuit including a variable element, a sampling deviceand a synchronism control circuit which operates to differentiate theoutput from the sampling device to vary the variable element, to stopthe variation of the variable element and to maintain the stoppedcondition, there is provided a control circuit responsive to thecessation of operation of either one of the synchronizing circuit or thesampling device to start either one of the synchronizing circuit,sampling device and the synchronism control circuit to continue to finda point of synchronism even in the absence of a synchronizing signal fora predetermined interval or even when the amplitude of the synchronizingsignal is small. A time axis circuit may be added which may becontrolled by the control circuit in the same manner.

2 Claims, 5 Drawing Figures SYNCHRONIZING CKT 12 3 SAMPLER FIG. I

g SYNCHRON I Z NG l5 CKT 2 SAMPLING SYNCHRONISM CKT CONT c FIG. 2

IYI FIG. 3 f

-6 CONT cKT IYImin SYNCHRONIZING 2 X0 CKT K l2 l3 2). S SYNCHRONISMSAMPLER r CONT CKT INVENTOR BY %w, 1 M, 6%

J L A I ATTORNEY SYNCHRONIZIE M CKT l3 i 9; K SAMPLER SYNCHRONISM CONTCKT F F u l6 SYNCHRONIZING TIME AXIS CKT CKT 6 l3 M 12 5 SAMPLERSYNCHRUNISM CKT CONT CKT I N VEN TOR ATTORNEY AUTOMATIC SYNCI-IRONIZINGSYSTEM CROSSREFERENCE TO RELATED APPLICATIONS This application isrelated to Applications Ser. No. 851,609, filed Aug. 20, 1969, entitledAUTOMATIC SYNCI-IRONIZING SYSTEMS FOR SAMPLING DE- VICES, now US. Pat.No. 3,633,066 issued on Jan. 4, 1972, and Ser. No. 851,588, filed Aug.20, I969, entitled AUTOMATIC SYNCl-IRONIZING SYSTEM, filed on even dateherewith.

BACKGROUND OF THE INVENTION This invention relates to a novel automaticsynchronizing system for apparatus requiring a synchronizing signal suchas an oscilloscope, a pulse generator and the like or a sampling devicesuch as a sampling oscilloscope, wherein an output pulse synchronizedwith a synchronizing signal input can be stably and automaticallyderived out and a point of synchronism can be automatically obtained bycontrolling a variable element in the synchronizing circuit even whenthe amplitude of the synchronizing signal input is small or there is nosuch signal input.

In the system of the type referred to above, as the frequency, amplitudeand waveform of the synchronizing input signal vary in various manner,in order to provide output pulses synchronized with'such various inputsignals it has been the practice to manually vary the synchronizinglevel of the signal inputs in the synchronizing circuit or to set thesynchronizing circuit in the self exciting condition to manually varyits frequency of self excitation. In other words, a variable elementsuch as voltage or current of the synchronizing circuit is varied bymanually adjusting it.

In order to obviate such troublesome manual adjustment, the applicantsfiled of even date herewith, a system outlined hereunder with referenceto FIGS. l and 2. As shown in FIGL 1, an input terminal 110 for thesynchronizing signal input is connected to a synchronizing circuit 111and the output of circuit Ill and the synchronizing signal input or asignal synchronized therewith are supplied to a sampling circuit 13 viaan input terminal 12 to provide a sampling signal of the input signal.The sampling signal is treated in a synchronism control circuit 14 tovary a variable element (not shown) in the synchronizing circuit 11 bythe output from the synchronism control circuit 14. Synchronism controlcircuit 14 operates to differentiate the sampling signal to stop thevariation of the variable element in the synchronizing circuit when theamplitude of the differentiated waveform becomes minimum whereby toautomatically maintain this condition. Assuming now that V(t) representsthe waveform that is sampled by sampling circuit 13 and maintainedthereby and that Y represents the differentiated value of V(t) withrespect to time, then Y will be shown by The absolute value of Y, thatis lYl becomes minimum when a point of synchronism is reached. When thevariable element included in the synchronizing circuit is varied fromits lower limit to its upper limit, or over its entire range, 1 Y1manifests its minimum value at a single point or a plurality of points.For the sake of description, FIG.2 shows a case wherein I Y] has asingle minimum value, but following explanation applies equallyirrespective of the number of minimum values of lYl.- In FIG. 2, theabscissa represents the variable element and the value of Xcorresponding to the minimum value of i Y] is represented by Xo. When Xis varied to obtain the minimum value of lYlmin or a value very closethereto and when Xis fixed to that point,

then the value of X will be very close to Xo. Under this condition, whensynchronism becomes out of step due to some variation in the parameter,for example, where the amplitude or frequency of the signalinput-varies, X begins to vary again to search the point of lYlmin or apoint very close thereto, and upon finding such point X is fixed to thatpoint. In this manner, the synchronism control circuit 14 operates toautomatically fix the value of X at or near lYlrnin.

If it is assumed now that X varies in a range of from Xa to X2 and thatin the range of from Xa to Xc (Xc Xz) the synchronizing circuit does notoperate in the absence of any synchronizing signal input but operatesupon reception of a synchronizing signal to generate a signalsynchronous therewith, and that the synchronizing circuit performs selfexcitation, even in the absence of the synchronizing signal, to generatea pulse in a range from Xc to Xz then between Xa and X0, the sensitivityof the circuit to the synchronizing-signal input decreases toward Xa. Inother words, the synchronizing circuit senses-only large synchronizingsignal inputs and increases its sensitivity from Xa to Xe. Further, fromXc to Xz, the synchronizing circuit operates to convert a receivedsynchronizing signal having a frequency higher than its frequency ofself excitation into a pulse of a frequency lower than a definitefrequency synchronous to said synchronizing frequency by the pull-inphenomenon.

In such a synchronizing circuit, if the amplitude of the synchronizingsignal input is small, in a range from Xa and Xb, (where Xb is anarbitrary value between Xa and Xc) there is a case wherein thesynchronizing circuit does not operate. When X is equal to Xa, as thesynchronizing circuit does not operate, no pulse will be generated.Accordingly, no sampled waveform V(t) and hence Y can be obtained. Thus,there is a defect that X is fixed to Xa so that the point of synchronismcan not be obtained.

SUMMARY OF THE INVENTION It is therefore an object of this invention toprovide a new and improved synchronizing system capable of controlling avariable element of a synchronizing circuit to find out a point ofsynchronism even when the amplitude of the synchronizing signal is smallor there is no synchronizing signal.

Another object of this invention is to provide an im provedsynchronizing system suitable for use in oscilloscopes, pulsegenerators, and sampling devices such as sampling oscilloscope whichrequire a synchronizing signal.

Briefly stated, in accordance with a preferred embodiment of thisinvention, there is provided an automatic synchronizing systemcomprising a synchronizing circuit including a variable element, asampling device, a synchronism control circuit which operates todifferentiate the output from the sampling device to vary the variableelement, to stop variation of the variable element upon reachingsynchronism and to maintain the stopped condition and a control circuitwhich senses stopping of operation of either one of the synchronizingcircuit and the sampling device to start either one of the synchronizingcircuit, sampling device and the synchronism control circuit to continueto find out a point of synchronism even in the absence of asynchronizing signal for a predetermined interval or even when theamplitude of the synchronizing signal is small.

According to amodified embodiment of this invention, a time axis circuitis added to the automatic synchronizing circuit which is similarlycontrolled by the control circuit.

BRIEF DESCRIPTION OF THE DRAWING The invention can be more fullyunderstood from the following detailed description taken in connectionwith the accompanying drawing in which;

FlG.l is a block diagram of an automatic synchronizing system, asdisclosed in applicants copending application;

FIG.2' show a graph to explain the principle of the automaticsynchronizing system;

FIGS. 3 and 4 are block diagrams illustrating different embodiments ofthis invention and FIG.5 shows a block diagram of a sampling device of asampling oscilloscope and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG.3illustrating a block diagram of this invention a control circuit 16 forcontrolling-synchronizing circuit 11 is added to the block diagram shownin FIGJ. The control circuit functions to initiate its operation whenthe synchronizing circuit 11 stops its operation for more than apredetermined interval to provide an output pulse for the synchronizingcircuit. For example, when the synchronizing circuit 11 stops itsoperation for more than 100 microseconds control circuit 16 operatesto'cause synchronizing circuit 11 to generatean output pulse of lOKHzevery 100 microseconds even when the amplitude of the synchronizingsignal applied to the synchronizing circuit is small or even when thereis no synchronizing signal. As a result, a sampler 13 causes thesynchronism control circuit 14 to operate to constantly find the pointof synchronism.

-FIG.4 shows a modified embodiment of this invention. In thisembodiment, in response to the cessation of operation of thesynchronizing circuit for more than a predetermined interval, controlcircuit 11 operates to start synchronism control circuit 14 to cause itto find out the point of synchronism even in the absence of thesynchronizing signal or even when the amplitude thereof is small.

Although not shown, the same object can also be accomplished byconstructing the control circuit .such that it will sense cessation ofthe operation of sampler 13 for more than a predetermined interval so asto start synchronizing circuit 16 or synchronism control circuit 14.

Although in the embodiment shown in FIGS control circuit 16 sensescessation of operation of the synchronizing circuit 11 to start thesame, the control circuit 16 may be arranged to start sampler 13 orsynchronism control circuit 14. In the same manner, the control circuit11 shown in FIG.4 can also be-arranged to start sampler 13 orsynchronism control circuit 14. Further, while in said two embodimentscontrol circuit 16 is constructed to sense stopping of operation of thesynchronizing circuit, according to this invention, control circuit 16can also be arranged to sense cessation of the operation of either oneof sampler 13 and synchronizing circuit 11 to start either one ofsynchronizing circuit ll, sampler l3 and synchronism control circuit.14.

Further, this invention is also applicable to a sampling device such asa sampling oscilloscope and the like. As shown in FIG.5, the blockdiagram of such a sampling device includes a time axis circuit 16interposed between the synchronizing circuit 11 and terminal 15 of FIG.1and, as a result, it is seen that the invention is applicable to such acircuit. In this case, the control circuit provided in accordance withthis invention is arranged to sense cessation of operation of at leastone of synchronizing circuit 11, sampler circuit 13 and item axiscircuit 16' to start either one of synchronizing circuit 11, samplingcircuit 13, time axis circuit 16' and synchronism control circuit 14.

Thus, according to this invention, in an automatic synchronizing systemwherein a variable element in a synchronizing circuit is variedautomatically by means of a synchronism control circuit and uponreaching synchronism the variation of the variable element is stoppedand that condition is maintained, a control circuit for effecting thecontrol function described above is provided thus enabling the point ofsynchronism even in the absence of the synchronizing signal over apredetermined interval or when the amplitude thereof is small. Thus thesynchronizing system of this invention can be used with advantages fordevices which require synchronizing signals such as an oscilloscope anda pulse generator as well as for sampling devices and the like.

Although the invention has been shown and described by illustratingpreferred embodiments thereof, it should be understood that theinvention is by no means limited to these particular embodiments butmany changes and modifications will occur to one skilled in the artwithout departing from the spirit and scope of the invention.

What is claimed is:

1. In an automatic synchronizing system having a synchronizing circuitincluding a variable element, a sampling device, and a synchronismcontrol circuit which operates to differentiate the output from saidsampling device to vary said variable element in said synchronizingcircuit, said synchronism control circuit further operating in responseto a minimum in said differentiated output to stop said variation ofsaid variable element upon reaching synchronism and to maintain thestopped condition, the improvement which comprises control circuit meansfor sensing stopping of operation of either one of said synchronizingcircuit and said sampling device and operablein response to saidstopping to start at least one of said synchronizing circuit, samplingdevice or said synchronism control circuit to continue to find a pointof synchronism even in the absence of a synchronizing signal for apredetermined interval or even when the amplitude thereof is small.

2. In a sampling device such as a sampling oscilloscope having asynchronizing circuit including a variable element, a sampling device, atime axis circuit and a synchronism control circuit which functions todifferentiate the output from said sampling device to vary said variableelement in said synchronizing circuit, said synchronizing controlcircuit also functioning in response to a minimum in said differentiatedoutput to stop said variation of said variable element upon reach- 6sampling device, synchronism control circuit or time axis circuit tocontinue to find a point of synchronism even in the absence of asynchronizing signal for a predetermined interval or even when theamplitude thereof is small.

UNITED STATES PATENT OFFICE CETIFICATE 0F CORRECTION PATENT NO.3,787,749

DATED January 22 1974 INVENTOR(S) KOZO Uchida, Naohisa Nakaya; KojiSuzuki it is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

In the legend, [73] Assignee: Iwata Electric Company, Tokyo, Japan"should read:

[73] Assignee: IWATSU ELECTRIC COMPANY, LTD. Tokyo, Japan Signed andSealed this second D 3.) Of September 19 75 [SEAL] A tres t:

RUTH C. MASON C. MARSHALL DANN r-trrtsling Officer (mnml'ssiunerufPauntrand Trademarks

1. In an automatic synchronizing system having a synchronizing circuit including a variable element, a sampling device, and a synchronism control circuit which operates to differentiate the output from said sampling device to vary said variable element in said synchronizing circuit, said synchronism control circuit further operating in response to a minimum in said differentiated output to stop said variation of said variable element upon reaching synchronism and to maintain the stopped condition, the improvement which comprises control circuit means for sensing stopping of operation of either one of said synchronizing circuit and said sampling device and operable in response to said stopping to start at least one of said synchronizing circuit, sampling device or said synchronism control circuit to continue to find a point of synchronism even in the absence of a synchronizing signal for a predetermined interval or even when the amplitude thereof is small.
 2. In a sampling device such as a sampling oscilloscope having a synchronizing circuit including a variable element, a sampling device, a time axis circuit and a synchronism control circuit which functions to differentiate the output from said sampling device to vary said variable element in said synchronizing circuit, said synchronizing control circuit also functioning in response to a minimum in said differentiated output to stop said variation of said variable element upon reaching synchronism and to maintain the stopped condition, and an automatic synchronizing system for said sampling device, the improvement comprising control circuit means for sensing stopping of operation of either one of said synchronizing circuit, sampling device and time axis circuit and operable in response to said stopping to start at least one of said synchronizing circuit, sampling device, synchronism control circuit or time axis circuit to continue to find a point of synchronism even in the absence of a synchronizing signal for a predetermined interval or even when the amplitude thereof is small. 